Control mechanism for varifocal objective

ABSTRACT

An objective with a varifocal front group and a varifocal rear group, separated by a pair of fixed lens members, is controlled by a mechanism including a common drive shaft coupled via respective gear sets with the two camming sleeves displacing the members of the respective varifocal groups. A diaphragm, interposed between the two fixed lens members, is adjusted jointly with the varifocal rear group through a mechanical linkage with the drive shaft or via an electronic programmer. In one embodiment, the presence of a differential gearing in cascade with the drive shaft along with detents on the two camming sleeves transmits the rotation of a control knob only to the front camming sleeve in a subrange of lesser focal lengths and only to the rear camming sleeve and the diaphragm in a subrange of greater focal lengths.

United States Patent [191 Korpert 1 w I CONTROL MECHANISM FCR VARIFOCAL OBJECTIVE Heinz Korpert, Bad Kreuznach, Rhineland, Germany Assignee: Jos. Schneider & Co Bad Kreuznach (Rhineland), Germany Filed: Dec. 5, 1973 Appl. N0.: 421,931

Inventor:

Foreign Application Priority Data Dec. 6, 1972 Germany 2259723 References Cited UNITED STATES PATENTS 3/1934 Durholz 354/196 12/1965 Mahn 354/196 12/1969 Thomas 354/196 11/1970 Barr 354/196 [451 July 22,1975

3,610,733 10/1971 Back 350/187 X Primary Examiner-Samuel S. Matthews Assistant Examiner-E. M. OConnor Attorney, Agent, or Firm--Karl F. Ross; Herbert Dubno [5 7] ABSTRACT An objective with a varifocal front group and a varifocal rear group, separated by apair of fixed lens members, is controlled by a mechanism including a common drive shaft coupled via respective gear sets with the two camming sleeves displacing the members of the respective varifocal groups. A diaphragm, interposed between the two fixed lens members, is adjusted jointly with the varifocal rear group through a mechanical linkage with the drive shaft or via an electronic programmer. In one embodiment, the presence of a differential gearing in cascade with the drive shaft along with detents on the two camming sleeves transmits the rotation of a control knob only to the front camming sleeve in a subrange of lesser focal lengths and only to the rear camming sleeve and the diaphragm in a subrange of greater focal lengths.

11 Claims, 6 Drawing Figures llllllllmfi H llllllll PATENTEDJUL 22 ms SHEET t mmomu L QM 1 CONTROL MECHANISM FOR VARIFOCAL OBJECTIVE FIELD OF THE INVENTION My present invention relates to a control mechanism for adjusting a varifocal objective used to take or reproduce pictures in photography, cinematography or television.

BACKGROUND OF THE INVENTION In commonly owned application Ser. No. 396,427, filed Sept. 12, 1973 by Karl Macher, there has been disclosed and claimed an objective of large varifocal ratio including an adjustable front lens group and an adjustable rear lens group of two components each, the two varifocal groups being separated by a fixed multilens component. Other fixed components are disposed forwardly of the first and rearwardly of the second varifocal group, an adjustable diaphragm (e.g. of the iris type) being inserted between these groups (i.e., between the third and fifth components) adjacent or within the fixed fourth component. The second and third components, forming part of the front group, are simultaneously axially shiftable at different rates in a first part of the varifocal range whereas the fifth and sixth components, forming part of the rear group, are similarly shiftable in a second part of that range. With the stationary first, fourth and seventh components positively refracting and with the second, third, fifth and sixth components negatively refracting, such a system may have an overall varifocal ratio fi f up to about :1.

The advantage of placing the diaphragm between the two varifocal groups, rather than on the image side of the rear group, is that the diameter of the front lens can be reduced without causing undesirable vignetting. In that case, however, any shift of the fifth and sixth components to increase the overall focal length is accompanied by a reduction of the exit pupil and therefore a decrease in relative aperture if the diaphragm opening remains constant. For this reason, as likewise disclosed and claimed in the commonly owned application referred to, the diaphragm should be adjusted concurrently with the varifocal rear group so that its opening increases along with the overall focal length to main-- OBJECTS OF THE INVENTION The general object of my present invention is to provide a single control mechanism for adjusting the two varifocal groups of such a system, or of any similar system with several components axially shiftable independently of one another in different parts of a range, whereby a user need not switch from one control to the other on crossing the boundary between the two subranges.

A more particular object, related to the preceding one, is to provide means for allowing thediaphragm to be independently (e.g.- manually) set to establish a se lected relative aperture which is maintained by the control mechanism throughout the varifocal range.

SUMMARY OF THE INVENTION In accordance with this invention I provide a first rotatable element, such as an internally grooved sleeve, cammingly engaged by the shiftable components of the front lens group and a second, similar rotatable element cammingly enaged by the shiftable components of the rear lens group, these two rotatable elements being mechanically coupled with a drive member (e.g. a manually operable knob) forming part of a common control mechanism for the two groups.

According to a more specific feature, the control mechanism is also operatively coupled with a diaphragm interposed between the two groups. as discussed above, for adjusting same upon rotation of the second camming element. This operative coupling may include an electronic programmer receiving position indications from the drive member or other parts of the control mechanism; alternately, the diaphragmadjusting means could be directly connected with that mechanism via a physical linkage such as a gear train. In an advantageous embodiment of the latter type. a shaft extends parallel to the optical axis along which the movable components are shiftable, this shaft being mechanically coupled with the diaphragm.

In principle, both pairs of movable components could be axially shifted throughout the entire range between the minimum focal length f and the maximum focal length f In order to simplify the optical calculations, however, and to allow the use of conventional varifocal groups in each half of the system, it is preferable to shift the components of the front groups only in a subrange from f to an intermediate focal length f and to shift the components of the rear group only in a complementary subrange from f to f,,,,,,. This alternate shifting can be accomplished by providing the camming formations of the two sleeves with extensions which lie in transverse planes so as to exert no camming effect upon the associated components even though the sleeve continues to rotate past the limit of its subrange.

In such ,a case the diaphragmicontrol mechanically linked with the sleeves should also be made ineffectual during part of the rotation Yof the common control shaft, i.e., in the subrange f m-f Another possibility is to decouple that shaft from the front sleeve by interposing a differential gearing between the drive member and the shaft, this gearing having another output cou- BRIEF DESCRIPTION OF THE DRAWING The above and other features of my invention will now be described in detail with reference to the accompanying drawing in which:

FIG. 1 is a side-elevational view, partly in axial sec- FIG. 3 is a cross-sectional view taken on the line Ill III of FIG. 2;

FIG. 4 diagrammatically illustrates an electronic coupling between a control member and an iris diaphragm in the system of FIG.-'l', i

FIG. 5 is a'developed view of two pairs of camming groovescarried by respective sleeves in the system of FIG. 1;

and

FIG. 6 shows a modified coupling between a control shaft and a diaphragm in the system of FIG. 1.

SPECIFIC DESCRIPTION In FIG. 1 I have shown a varifocal optical system, generally similar to that disclosed in the aforementioned Macher application Ser. No. 396,427, with seven coaxial components, i.e., a substantially fixed front component 7 (which may be limitedly axially shiftable for focusing purposes), a movable negative second ,componentll, a movable negative third component 12, a fixed fourth component consisting of two axially separated lens members 8 and 9, a movable negative fifth component 13, a movable negative sixth component 14, and a fixed seventh component 10. Components 1 1 and 12 are provided with studs 11a and 12a guided in respective camming grooves 3 and 4 of a sleeve 1 rotatable about the optical axis of the system. Similar studs 13a and 14a on components 13 and 14 engage in respective camming grooves and 6 of another such sleeve 2. Sleeves 1 and 2 have toothed flanges 22 and 23 in mesh with respective pinions 19 and 20 on a shaft '21 extending parallel to axis 0; shaft 21 is rotatable by a gear 18 on a stub shaft 45 engaging the pinion .19. Shaft 45 maybe manually driven by means of a knob 49 (FIG. 4) or may be coupled with an automatic zoom control not shown.

Another pinion 28 on shaft 21 meshes with a pinion ,29 on an ancillary shaft 46 which in turn engages a set generally helicoidal camming grooves 3, 4, 5 and 6 have beenshown in developed form. As illustrated by way of example in full lines, grooves 3 and 4 are curved over part of their length, equaling a fraction of the cir- 'curnference of sleeve 1, which corresponds to a lower subrange fmi7| f these grooves have upward extensions of zero pitch and therefore without camming function whose length equals another fraction of the sleeve circumference and corresponds to an upper subrange f f,,.,, Thus, components 11 and 12 are axially shifted in the lower subrange, at different rates and partly in opposite directions, but are held stationary in the upper subrange; conversely, components 13 and 14 are held stationary in the lower subrange by zero pitch portions of curves 5 and 6 and are shifted independently in the upper subrange.

' Since the mechanism shown in FIG. 1 drives the sleeves 1 and 2 at different rates, on account of the different transmission ratios between gear pairs 19, 22

aiid' 20, 23, it will be evident that the grooves 3 and 4 extend over a smaller arc in sleeve 1 than do grooves 5 and 6 in sleeve 2 in order that their extremities should coincide in the limiting angular positions of the varifocal range, i.e., in positions: f,",.,-,,'and fmmr as shown in FIG. 5. For easier comparison, however, this difference in arc length hasbeen disregarded in the developed view of FIG. 5.

As indicated in dot-dashlines in FIG. 5, these camming grooves could also be modified so that theircurvatures extend over the full varifocal range f -f,,,,,,; the limiting positions of all four components for f=f,,, and f f are the same in both instances.

With the mechanical coupling between shaft 21 and mounting ring 17 illustrated in'FIG. l, diaphragm 15 17 is continuously adjusted to compensate for the shift of components 13 and 14 according to the phantomline curvature of the camming grooves. With components l3 and 14 held stationary in the lower subrange, by a shaping of the grooves as shown in full lines, the coupling between shaft 21 and ring 17 should be modified so that the ring is also held stationary in the-lower subrange and entrained only in the upper one. This has been illustrated in FIG. 6 where the pinion 28 with its full complement of teeth has been replaced by a gear 28"on shaft 21 having only a partially toothed periphery; the coacting mounting ring 17 also has only a few teeth so positioned that the smooth periphery of gear 28' holds the ring stationary during part of a shaft revolutionwhereas the teeth of the gear engage with those of the ring to rotate the latter during another part of that revolution. Iris leaves 15 (only one shown) are pivoted to rings 16 and 17' at51 and 52, respectively; the rotary entrainment of ring 17' in a clockwise direction swings the leaves outwardly to enlarge the diaphragm opening. It will be apparent that the size of this opening may be preselected independently of the position of mounting ring 17 by adjustment of setting ring 16.

Whatever the shape of the camming groove s 3 6,

diaphragm 15 17 may be controlled electronically (rather than mechanically as in FIGS. 1 and 6) with the aid of a programmer as illustrated in FIG. 4. Thus, rotation of shaft 45 and gear 18 by knob 49 into any selected focal-length position signals that position to the programmer which thereupon rotates the shaft 46 of pinion 29 ,into a corresponding position, the mating pinion 28 on shaft 21 being omitted in this case.

The system shown in FIG. 2 differs from that of FIG. 1 mainly by the substitution of a differential gearing 53 for the pinion 19, this gearing comprising two coaxial spurgears 31, 33 idling on shaft 21 and a transverse stud 32 rigid with that shaft carrying a pairv of bevel gears 54, freely rotatable thereon. Gears 31 and 33 have beveled sets ofv teeth 31a and 33a meshing with both bevel gears 54 and 55. Gear 31 thus acts asan input of differential gearing 53 whose two outputs are gear 33 and shaft 21. Gear 33 meshes with the teeth 22 of sleeve 1 which in this instance carries an arcuate rib 56 coacting with a fixed stop 39 to define a limited range of rotation of that sleeve. A similar arcuate rib 57 on sleeve 2 coacts with a fixed stop 40. Furthermore, sleeve 1 has an annular ridge 43 formed with a notch 41 which is engageable by a detent in the form of a roller 37 on a spring-loaded arm 34 pivoted on a shaft 36 (see also FIG. 3); a similar spring-loaded arm 35 on the same shaft 36 carries a roller 38 engageable with a notch 42 of an annular ridge 44 of sleeve 2.

. M transmission 18, 53, 2l'of FIG. 2 is so arranged that with gear-18 turning u nidirectionally in a predetermined'sense, sleeve 1 tends to move counterclockwise and sleeve 2 tends to move clockwise as indicated by the arrows in FIG. 3. In the starting position f f,,,,,, illustrated in FlGS. 2 and 3, sleeve 1 is free to rotate but sleeve 2 is arrested by the detent roller 38 engaging in notch 42. After a rotation of a little more than 90, rib 56 comes to rest against stop 39 in the intermediate position f f,,,,,,,. With sleeve 1 and gear 33 stopped, fur ther turning of shaft 45 in the same sense exerts an overriding force on shaft 21 which disengages the roller 38 from the ridge 44 so that sleeve 2 can now rotate through about 120 until its rib 57 strikes the stop 40 from the opposite side; this is the terminal position f During the return stroke, sleeve 1 is initially immobilized by the.roller 37 which entered the notch 41 of its ridge 43 in the intermediate position f f When this position is again reached, sleeve 2 is arrested by contact of its rib 57 with stop 40 (and is simultaneously indexed against reverse rotation by roller 38 reengaging in notch 42) while roller 37 is cammed out of its notch 41 to release the sleeve 1 for clockwise rotation back to the starting position.

Since in the system of FIG. 2 the sleeves l and 2 rotate in opposite directions during unidirectional rotation of drive shaft 45, the curvature of camming grooves 5 and 6 will have to be inverted in comparison with FIG. 1.

Reference may be made to the aforementioned Macher application, particularly Tables ll, IIA and 11B thereof, for suitable optical parameters of an objective having the varifocal ratio f fmin 30:1.

I claim:

1. A varifocal objective comprising:

a front lens group centered on an axis including a first pair of shiftable components each movable along said axis at a rate different from that of the other component;

a rear lens group coaxial with said front lens group including a second pair of shiftable components each movable along said axis at a rate different from that of the other component;

a first rotable element;

first cam means operatively connecting said first rotatable element with said first pair of components; a second rotatable element; second cam means operatively connecting said second rotatable element with said second pair of components; and a common control mechanism for all said components including a rotatable drive member mechanically coupled with both said elements for rotating same.

2. A varifocal objective as defined in claim 1, further comprising a diaphragm of variable aperture provided with adjusting means and coaxially interposed between said front and rear lens groups, said control mechanism being operatively coupled with said adjusting means for changing said aperture upon rotation of said second element.

3. A varifocal objective as defined in claim 2 wherein said control mechanism includes a shaft extending parallel to the axis of said components, said diaphragm being mechanically coupled with said shaft.

4. A varifocal objective as defined in claim 3 wherein said shaft is provided with first gear means engaging said first element, second gear means engaging said second element and third gear means engaging said dia phragm.

5. A varifocal objective as defined in claim 4 wherein said adjusting means includes a mounting ring coupled with said third gear means and a setting ring coaxially spaced from said mounting ring, said diaphragm having a set of iris leaves pivoted to both said rings, said setting ring being rotatable independently of said mounting ring.

6. A varifocal objective as defined in claim 4 wherein said first cam means comprises formations on said first element effective to shift said first pair of components only during a first phase of angular displacement of said shaft, said second cam means comprising formations on said second element effective to shift said second pair of components only during a second phase of angular displacement of said shaft.

7. A varifocal objective as defined in claim 6 wherein said adjusting means is ineffectual to change said aperture in said first phase of angular displacement.

8. A varifocal objective as defined in claim 3 wherein said control mechanism includes differential gearing having an input coupled with said drive member, a first output coupled with said first element and a second output coupled with said shaft, the shaft being in positive engagement with said diaphragm and with said second element.

9. A varifocal objective as defined in claim 8 wherein said elements are provided with detents for releasably arresting said first element in a second phase and said second element in a first phase of angular displacement of said shaft.

10. A varifocal objective comprising:

a front lens group centered on an axis including a first pair of shiftable components each movable along said axis at a rate different from that of the other component;

a rear lens group coaxial with said front lens group including a second pair of shiftable components each movable along said axis at a rate different from that of the other component; and

drive means rotatable about said axis within a range I of angular positions divided into a first and a second subrange, said drive means being provided with a first pair of generally helicoidal camming formations respectively engaging said first pair of components and with a second pair of generally helicoidal camming formations respectively engaging said second pair of components, said first pair of camming formations having portions of zero pitch engaging said first pair of components in said first subrange, said second pair of camming formations having portions of zero pitch engaging said second pair of components in said second subrange.

11. A varifocal objective as defined in claim 10 wherein said drive means comprises a first sleeve centered on said axis and provided with said first pair of camming formations, a second sleeve centered on said axis and provided with said second pair of camming formations, and transmission means for jointly rotating said sleeves at different rates. 

1. A varifocal objective comprising: a front lens group centered on an axis including a first pair of shiftable components each movable along said axis at a rate different from that of the other component; a rear lens group coaxial with said front lens group including a second pair of shiftable components each movable along said axis at a rate different from that of the other component; a first rotable element; first cam means operatively connecting said first rotatable element with said first pair of components; a second rotatable element; second cam means operatively connecting said second rotatable element with said second pair of components; and a common control mechanism for all said components including a rotatable drive member mechanically coupled with both said elements for rotating same.
 2. A varifocal objective as defined in claim 1, further comprising a diaphragm of variable aperture provided with adjusting means and coaxially interposed between said front and rear lens groups, said control mechanism being operatively coupled with said adjusting means for changing said aperture upon rotation of said second element.
 3. A varifocal objective as defined in claim 2 wherein said control mechanism includes a shaft extending parallel to the axis of said components, said diaphragm being mechanically coupled with said shaft.
 4. A varifocal objective as defined in claim 3 wherein said shaft is provided with first gear means engaging said first element, second gear means engaging said second element and third gear means engaging said diaphragm.
 5. A varifocal objective as defined in claim 4 wherein said adjusting means includes a mounting ring coupled with said third gear means and a setting ring coaxially spaced from said mounting ring, said diaphragm having a set of iris leaves pivoted to both said rings, said setting ring being rotatable independently of said mounting ring.
 6. A varifocal objective as defined in claim 4 wherein said first cam means comprises formations on said first element effective to shift said first pair of components only during a first phase of angular displacement of said shaft, said second cam means comprising formations on said second element effective to shift said second pair of components only during a second phase of angular displacement of said shaft.
 7. A varifocal objective as defined in claim 6 wherein said adjusting means is ineffectual to change said aperture in said first phase of angular displacement.
 8. A varifocal objective as defined in claim 3 wherein said control mechanism includes differential gearing having an input coupled with said drive member, a first output coupled with said first element and a second output coupled with said shaft, the shaft being in positive engagement with said diaphragm and with said second element.
 9. A varifocal objective as defined in claim 8 wherein said elements are provided with detents for releasably arresting said first element in a second phase and said second element in a first phase of angular displacement of said shaft.
 10. A varifocal objective comprising: a front lens group centered on an axis including a first pair of shiftable components each movable along said axis at a rate different frOm that of the other component; a rear lens group coaxial with said front lens group including a second pair of shiftable components each movable along said axis at a rate different from that of the other component; and drive means rotatable about said axis within a range of angular positions divided into a first and a second subrange, said drive means being provided with a first pair of generally helicoidal camming formations respectively engaging said first pair of components and with a second pair of generally helicoidal camming formations respectively engaging said second pair of components, said first pair of camming formations having portions of zero pitch engaging said first pair of components in said first subrange, said second pair of camming formations having portions of zero pitch engaging said second pair of components in said second subrange.
 11. A varifocal objective as defined in claim 10 wherein said drive means comprises a first sleeve centered on said axis and provided with said first pair of camming formations, a second sleeve centered on said axis and provided with said second pair of camming formations, and transmission means for jointly rotating said sleeves at different rates. 